MRAM,spintronics

1. Spintronics
Govt.engg.college Ajmer
Guided By:- Ms. Kajal Bhadel Submitted By:- Khushal Yadav
Roll No:- 09EI20

2. Introduction
Conventional electronic devices ignore
the spin property and rely strictly on the
transport of the electrical charge of
electrons
Adding the spin degree of freedom
provides new effects, new capabilities and
new functionalities

3. Disadvantages of electronics
 High power consumption.
 High heat dissipation.
 Electronics memory is volatile.
 Takes up higher space on chip, thus less compact.
 Electron manipulation is lower , so poor read & write speed.
Electronics require unique and specialized semiconductors materials.
 Common metals such as Fe, Al, Ag , etc. can’t be used.

4. Future Demands
Moore’s Law states that the number of transistors on a silicon chip will
roughly double every eighteen months
By 2008, it is projected that the width of the electrodes in a
microprocessor will be 45nm across
As electronic devices become smaller, quantum properties of the wave
like nature of electrons are no longer negligible
Spintronic devices offer the possibility of enhanced functionality, higher
speed, and reduced power consumption

5. Computational benefits
Simple device structure for high degree of integration and high process yield.
Large magnetocurrent for high speed operation
High transconductance for high speed operation
High amplification capability (V, I, and/or power)
Hyperthreading enchancment
Bit vs. qubit

6. Comparison of spintronics with electronics

7. Electronics v/s Spintronics
 One of the main advantage of spintronics over electronics is
the magnets tend to stay magnetize which is sparking in the
industry an interest for replacing computer’s semiconductor
based components with magnetic ones, starting with the RAM.
 With an all-magnetic RAM, it is now possible to have a
computer that retains all the information put into it. Most
importantly, there will be no ‘boot-up’ waiting period when
power is turned on.

8.  Another promising feature of spintronics is that it doesn’t
require the use of unique and specialized semiconductor, there
by allowing it to work with common metals like Cu, Al, Ag.
 Spintronics will use less power than conventional electronics,
because the energy needed to change spin is a minute fraction
of what is needed to push charge around.

9. Conventional Electronics
Metal Gate
n+ n+
Ohmic contact Ohmic Contact
P-type Si
Oxide
Electron
Inversion layer
Metal Oxide Semiconductor Field Effect Transistor
MOSFET
Gate Voltage changes electron density
changes conductivity

10. Spintronics
Inject polarized spin from one FM contact -- modulate current by
modifying spin precession via Rashba effect
Spin Transistor
Schottky GateFM Metal FM Metal
InGaAs
Modulation Doped AlGaAs
2DEG
Spin
Analyzer
B
Spin
Injector

11. Principal of spintronics
 Spintronics is based on the spin of electrons rather than its charge.
 Every electron exist in one of the two states- spin-up and spin-down,
with spins either positive half or negative half.
 In other words, electrons can rotate either clock wise or anti-clockwise
around its own axis with constant frequency.
 The two possible spin states represent ‘0’ and ‘1’ in logical operations.

12. Combining the best of both worlds
Ferro magnets
• Stable Memory
• Fast switching
• High ordering temp
• Spin transport
• Technological base
(magnetic recordings)
Semiconductors
• Bandgap engineering
• Carrier density & type
• Electrical gating
• Long spin lifetime
• Technological base
(Electronics)
develop spin based transistors ,
switches and logic circuits?
create control propagate spin
information in semiconductor
structures?

13. Advantages of Spin
 Information is stored into spin as one of two possible orientations
Spin lifetime is relatively long, on the order of nanoseconds
 Spin currents can be manipulated
 Spin devices may combine logic and storage functionality
 eliminating the need for separate components
 Magnetic storage is nonvolatile
 Binary spin polarization offers the possibility of applications as

14.  Spin is a characteristic that makes an electron a tiny magnet with north and
south poles.
 The orientation of north-south axis depends on the particle’s axis of spin.
 In ordinary materials, the up magnetic moments cancel the down magnetic
moment so no surplus moment piles up.
 Ferro-magnetic materials like iron, cobalt and nickel is needed for
designing of spin electronic devices.

15. Terminology in Spintronics
1. GMR
2. Spin Valve
3. Spin Transistor
4. Spin Transfer
5. AMR
6. TMR

16. Giant MagnetoResistive (GMR)
1988 France, GMR discovery is accepted as birth of
spintronics
A Giant MagnetoResistive device is made of at least
two ferromagnetic layers separated by a spacer layer
When the magnetization of the two outside layers is
aligned, lowest resistance
Conversely when magnetization vectors are
antiparallel, high R
Small fields can produce big effects
parallel and perpendicular current

19. Spin Valve
Simplest and most successful spintronic device
Used in HDD to read information in the form of small
magnetic fields above the disk surface

20. Datta Das Spin Transistor
The Datta Das Spin Transistor was first
spin device proposed for metal-oxide
geometry, 1989
Emitter and collector are ferromagnetic
with parallel magnetizations
The gate provides magnetic field
Current is modulated by the degree of
precession in electron spin

21. Spin Transfer
V
The spin of the
conduction electron
is rotated by its
interaction with the
magnetization.
This implies the magnetization exerts a torque on the spin. By
Conservation of angular momentum, the spin exerts an equal and
Opposite torque on the magnetization.
<S>
v
2M1M

22. Experimental Proof of Spin Transfer
I
Predicted theoretically
by Slonczewksi and
Berger in 1996
I
I
P
AP

23. Anisotropic magnetoresistance (AMR)
 Property of a material in which a dependence of electrical resistance
on the angle between the direction of electric current and direction of
magnetization is observed

24. Tunnel magnetoresistance(TMR)
 Tunnel magnetoresistance (TMR) is a magnetoresistive effect that
occurs in a magnetic tunnel junction (MTJ), which is a component
consisting of two ferromagnets separated by a thin insulator.

25. Click to edit Master text styles
Second level
● Third level
● Fourth level
● Fifth level
WHICH MATERIAL GIVES
OPTIMISTIC VALUE

26. (MRAM)
Magneto resistive RAM
Reading process(ON-State)
 Measurement of the bit cell
resistance by applying a
current in the ‘bit line’
 Comparison with a reference
value mid-way between the
bit high and low resistance
values

27. Writing process(Off-State)
 Currents applied in both lines : 2
magnetic fields
 Both fields are necessary to
reverse the free layer
magnetization
 When currents are removed :
Same configuration

28. MRAM vs …..

29. Spintronics capabilities
(1) Hard drives up to 1.2 petabytes with compact capability

30. Conclusion
 Interest in spintronics arises, in part, from the looming problem
of exhausting the fundamental physical limits of conventional
electronics.
 However, complete reconstruction of industry is unlikely and
spintronics is a “variation” of current technology
 The spin of the electron has attracted renewed interest because it
promises a wide variety of new devices that combine logic,
storage and sensor applications.
 Moreover, these "spintronic" devices might lead to quantum
computers and quantum communication based on electronic
solid-state devices, thus changing the perspective of information
technology in the 21st century.

31. Queriess…….